This invention relates to new macrolide antibiotics with improved activity and stability, to the use of such antibiotics for the treatment of infectious diseases and to compositions containing such macrolides.
The interest in macrolide antibiotics is increasing because these compounds are a very effective and safe class of agents against gram positive pathogens. Extensive spread of erythromycin A resistance among gram positive cocci isolates raised the urgent need for novel derivatives with improved activity, stability and antimicrobial spectra. The two most successful second generation agents derived from erythromycin A (1) through semisynthesis were its 6-O-methyl derivative clarithromycin (2) and the 15-membered azalide azithromycin (3) arising from a Beckman rearrangement as shown below. However, while featuring improved pharmacokinetics, none of these agents possessed a significant activity against bacterial isolates showing macrolide-lincosamide-streptogramine B (MLS B) cross resistance. 
Many different semisynthetic third generation derivatives of the ketolide class of macrolide antibiotics have been described, the most potent being HMR 3647 or telithromycin (4) (EP 680967 A1 (1995); FR 2732684 A1 (1996); Bioorg. Med. Chem. Lett. (1999), 9(21), 3075-3080.) and ABT 773 (WO 9809978 (1998); J. Med. Chem. 2000, 43, 1045). However, none of these agents described thus far have been able to overcome constitutive MLS B resistance in Staphylococcus aureus. 
The invention provides new macrolide antibiotics of formula I with improved biological properties and improved stability. 
wherein
R1 is hydrogen, cyano, xe2x80x94S(L)mR2, xe2x80x94S(O)(L)mR2, or xe2x80x94S(O)2(L)mR2;
L represents xe2x80x94(CH2)nxe2x80x94 or xe2x80x94(CH2)nZ(CH2)nxe2x80x2xe2x80x94;
m is 0 or 1;
n is 1, 2, 3, or 4;
nxe2x80x2 is 0, 1, 2, 3, or 4;
Z is O, S or NH;
R2 is hydrogen, alkyl, heterocyclyl or aryl; which heterocyclyl and the aryl groups may be further substituted;
* indicates a chiral center which is in the (R) or (S) form.
and pharmaceutically acceptable acid addition salts or in vivo cleavable esters thereof.
These compounds are new and possess potent antimicrobial properties against gram positive and selected gram negative organisms. Therefore, they are useful as agents against gram positive pathogens such as staphylococci, streptococci and pneumococci as well as some gram negative strains such as H. influenzae and may be used in human or veterinary medicine for treatment or prevention of infections caused by susceptible organisms.
The chiral center in position 3 is preferably in the (S) whereas the center in 4 are is preferably in the (R) configuration.
As used herein the term xe2x80x9calkylxe2x80x9d refers to straight or branched chain saturated hydrocarbon group having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms. Such groups are for example methyl, ethyl, n-propyl, isopropyl, tertiary butyl, pentyl, hexyl, and the like.
The term xe2x80x9chalogenxe2x80x9d refers to chlorine, bromine or iodine.
The term xe2x80x9carylxe2x80x9d refers to 6-membered, aromatic groups with one or more nuclei from 6 to 14 carbon atoms. Examples are phenyl, naphthyl, anthryl and phenanthryl. These groups may be further substituted with, for example, phenyl, alkyl, lower alkoxy such as methoxy, ethoxy, propyloxy or n-butoxy, halogen, hydroxy, amino, alkylamino, dialkylamino or nitro.
As used herein the term xe2x80x9cheterocyclylxe2x80x9d refers to an unsaturated or saturated, unsubstituted or substituted 5-, 6-, or 7-membered (mono- or bicyclic) heterocyclic ring system containing at least one hetero atom selected from the group consisting of oxygen, nitrogen, and/or sulfur. Exemplary heterocyclic substituents include, but are not limited to, for example, the following groups:
piperidinyl, morpholinyl, 2-, 3- or 4-pyridyl, pyrrolidinyl, piperazinyl, 1H-pyrazol-1-yl, 1H-[1,2,4]triazol-1-yl, 1H-imidazol-1-yl, pyrazinyl, pyrimidyl, pyridazinyl, pyrazolyl, triazinyl, thiazolyl, thiadiazolyl, oxadiazolyl, triazolyl, 1H-tetrazolyl, 2H-etrazolyl; thienyl, furyl, 1H-azepinyl, tetrahydrothiophenyl, 3H-1,2,3-oxathiazolyl, 1,2,3-oxadiazolyl, 1,2,5-oxadithiolyl, isoxazolyl, isothiazolyl, 4H-1,2,4-oxadiazinyl, 1,2,5-oxathiazinyl, 1,2,3,5-oxathiadiazinyl, 1,3,4-thiadiazepinyl, 1,2,5,6-oxatriazepinyl, 1,6,3,4-dioxadithiopanyl, oxazolidinyl, tetrahydrothienyl, and the like, or condensed heterocyclic ring systems such as quinolinyl, isoquinolinyl, quinazolinyl, 1H-benztriazolyl, 1H-imidazo[4,5-c]pyridinyl, 5H-imidazo[4,5-c]pyridinyl, 1H-imidazo[4,5-b]pyridin-1-yl, 3H-imidazo[4,5-b]pyridin-3-yl, 1,2,3,4-tetrahydro-isoquinolinyl, thieno[2,3-b]pyridinyl, benzothiazolyl, 1H-benzoimidazolyl, 1H-indolyl, 1,2,3,4-tetrahydroquinolinyl, purinyl, e.g. 9H-purin-9-yl, 6-amino-9H-purin-9-yl, and others.
The aryl or heterocyclyl groups may be further substituted by one or more substituents. Such substituents include, for example, alkyl groups such as defined above, alkoxy groups such as methoxy, ethoxy, propyloxy or butyloxy, halogen such as fluorine, chlorine, bromine or iodine, halogen substituted alkyl groups such as trifluoromethyl, trichloroethyl, nitro, amino, alkylamino, dialkylamino, alkylthio, mercapto, hydroxy, carbamoyl, a carboxyl group, an oxo group; or unsubstituted or substituted aryl as defined above; or heterocyclyl.
Especially preferred substituents for the heterocyclic groups are alkyl, alkoxy, oxo, amino, alkylamino or dialkylamino. Examples of preferred substituted heterocyclic rings are 1H-pyrimidin-2,4-dione-1-yl, 1H-pyrimidin-2,4-dione-5-methyl-1-yl, 1H-pyrimidin-4-amino-2-one-1yl, 6-amino-9H-purine-9-yl, 6-dimethylamino-9H-purine-9-yl, 3-(pyridin-3-yl)-1H-pyrazol-1-yl, 3-(pyridin-4-yl)-1H-pyrazol-1-yl, 3-(pyridin-3-yl)-1H-imidazol-1-yl, 3-(pyridin-4-yl)-1H-imidazol-1-yl, 3-(pyridin-3-yl)-1H-[1,2,4]triazol-1-yl, or 3-(pyridin-4-yl)-1H-[1,2,4]triazol-1-yl.
Preferred compounds of formula I are compounds, wherein L is xe2x80x94(CH2)n and n is 0, 1, 2 or 3. Further preferred are compounds of formula I, wherein R2 is aryl or heterocyclyl, especially, wherein R2 is phenyl, dialkoxyphenyl, 6-amino-9H-purin-9-yl or pyridinyl-1H-pyrazol-1-yl.
Especially preferred compounds of formula I are in Table 1 below:
If desired, compounds of formula I can be converted into a pharmaceutically acceptable acid addition salt. The salt formation is effected at room temperature with methods which are known per se and which are familiar to any person skilled in the art. Not only salts with inorganic acids, but also salts with organic acids come into consideration. Hydrochlorides, hydrobromides, sulfates, nitrates, citrates, acetates, trifluoroacetates, maleates, succinates, methanesulphonates, p-toluenesulphonates and the like are examples of such salts.
Further the compounds can be converted into in vivo cleavable esters, for example into esters with the 2xe2x80x2-hydroxy group of the sugar moiety, such esters are e.g. acetates, pivaloyl esters, tartrates, maleates, succinates, and the like. These esters can be prepared according to methods known in the art, for example by reaction with an appropriate anhydride.
The compounds of the present invention and their pharmaceutically acceptable acid addition salts or in vivo cleavable esters thereof are useful as antibacterial therapeutics. Compounds of formula I possess excellent antibacterial activity against selected pathogenic bacteria such as strains of Staphylococcus aureus and Streptococcus pneumoniae. They can thus be used as medicaments for the treatment of infectious diseases especially of infectious diseases caused by staphylococci, such as septicemia, skin infections, soft tissue infections, deep infections after trauma, surgery or insertion of foreign material, pneumonia, arthritis, bursitis, and osteomyelitis, infections caused by streptococci such as septicemia, skin infections, soft tissue infections, deep infections after trauma, surgery or insertion of foreign material, pharyngitis, pneumonia, bronchopneumonia, bronchitis, otitis, sinusitis, and scarlet-fever.
Furthermore, the compounds of formula I can be used as medicaments for the treatment of infections caused by germs such as Haemophilus influenzae, Moraxella catarrhalis, rickettsiae, ehrlichiae, Mycoplasma pneumoniae, Neisseria spp., Chlamydia spp, Legionella spp, Ureaplasma urealyticum or by susceptible strains of Mycobacterium spp.
The antibacterial activities of the compounds have been determined by standard microdilution technique (National Committee for Clinical Laboratory Standards. 1997. Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically, 4th edition. Approved standard M7-A4. National Committee for Clinical Laboratory Standards, Wayne, Pa.). The activities expressed as the minimum inhibitory concentrations (MICs) (xcexcg/ml) are given in Table 2 below.
The biological activities of compounds of the present invention against Haemophilus influenzae have been determined by standard agar dilution method using HTM medium (National Committee for Clinical Laboratory Standards. 1997. Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically, 4th edition. Approved standard M7-A4. National Committee for Clinical Laboratory Standards, Wayne, Pa.). Their MICs along with MIC""s of selected reference compounds are given in Table 3.
The compounds in accordance with the invention can be used as medicaments. They possess good oral absorption properties. A further embodiment of the present invention are thus medicaments comprising compounds of formula I, their pharmaceutically acceptable acid addition salts or in vivo cleavable esters thereof for the treatment and prevention of infectious diseases, for example, in the form of pharmaceutical preparations for enteral (oral) administration. The products in accordance with the invention can be administered, for example, perorally, such as in the form of tablets, coated tablets, dragees, hard and soft gelatin capsules, solutions, emulsions or suspensions, or rectally, such as in the form of suppositories, or parenterally e.g. by injection, or locally for example by topical administration, preferably the compounds are administered orally.
Pharmaceutical compositions containing these compounds can be prepared using conventional procedures familiar to those skilled in the art, such as by combining the ingredients into a dosage form together with suitable, non-toxic, inert, therapeutically compatible solid or liquid carrier materials and, if desired, the usual pharmaceutical adjuvants.
It is contemplated that the compounds are ultimately embodied into compositions of suitable oral, parenteral or topical dosage forms. The compositions of this invention can contain, as optional ingredients, any of the various adjuvants which are used ordinarily in the production of pharmaceutical preparations. Thus, for example, in formulating the present compositions into the desired oral dosage forms, one may use, as optional ingredients, fillers, such as coprecipitated aluminum hydroxide-calcium carbonate, dicalcium phosphate or lactose; disintegrating agents, such as maize starch; and lubricating agents, such as talc, calcium stearate, and the like. It should be fully understood, however, that the optional ingredients herein named are given by way of example only and that the invention is not restricted to the use hereof. Other such adjuvants, which are well known in the art, can be employed in carrying out this invention.
Suitable as such carrier materials are not only inorganic, but also organic carrier materials. Thus, for tablets, coated tablets, dragees and hard gelatin capsules there can be used, for example, lactose, maize starch or derivatives thereof, talc, stearic acid or its salts. Suitable carriers for soft gelatin capsules are, for example, vegetable oils, waxes, fats and semi-solid and liquid polyols (depending on the nature of the active substance; no carriers are, however, required in the case of soft gelatin capsules). Suitable carrier materials for the preparation of solutions and syrups are, for example, water, polyols, saccharose, invert sugar and glucose. Suitable carrier materials for suppositories are, for example, natural or hardened oils, waxes, fats and semi-liquid or liquid polyols.
As pharmaceutical adjuvants there are contemplated the usual preservatives, solubilizers, stabilizers, wetting agents, emulsifiers, sweeteners, colorants, flavorings, salts for varying the osmotic pressure, buffers, coating agents and antioxidants.
The compounds of formula I and their acid addition salts or in vivo cleavable esters thereof can be used for parenteral administration and for this purpose are preferably made into preparations for injection as lyophilisates or dry powders for dilution with customary agents, such as water or isotonic common salt solution.
The compounds of formula I and their acid addition salts or in vivo cleavable esters thereof can be used for topical administration and for this purpose are preferably made into preparations as ointments, cremes or gels.
For the prevention and treatment of infectious diseases in mammals, human and non-human, a daily dosage of about 10 mg to about 2000 mg, especially about 50 mg to about 1000 mg, is usual, with those of ordinary skill in the art appreciating that the dosage will depend also upon the age, conditions of the mammals, and the kind of diseases being prevented or treated. The daily dosage can be administered in a single dose or can be divided over several doses. An average single dose of about 100 mg, 250 mg, 500 mg and 1000 mg can be contemplated.
The compounds of the present invention can be prepared by method well known in the art, e.g. by chemical modification of the readily available template molecule 2xe2x80x2-O-acetyl-4xe2x80x3-O-benzyloxy-carbonyl-6-O-methyl-11-deoxy-10,11-didehydroerythromycin A (6) 
first described by Baker et al. in J. Org. Chem. 1988, 53, 2340-2345. The template molecule (6) was synthesized by means of modified procedures published by Baker et al. in J. Org. Chem. 1988, 53, 2340-2345 and Agouridas et al. in J. Med. Chem. 1998, 41, 4080-4100, i.e. starting from the semisynthetic 6-O-methyl derivative clarithromycin (2) according to the procedure depicted in Scheme 1. 
Scheme 1: Reagents and conditions: a) Ac2O, CH2Cl2, room temp; b) PhCH2OCOCl, DMAP, CH2Cl2, xe2x88x9230xc2x0 C.; c) NaHMDS, 1,1xe2x80x2-carbonyldiimidazole (CDI), THF, xe2x88x9278xc2x0 C.; d) DBU, benzene, reflux.
The 2xe2x80x2-hydroxy group of the desosamine moiety of clarithromycin (2) was selectively protected by treatment with acetic anhydride in methylene chloride without addition of base to give compound 7 in near quantitative yield. Subsequently, a benzyloxycarbonyl protecting group was introduced selectively to the 4xe2x80x3-hydroxy group by treatment of 7 with benzyl chloroformiate and 4-dimethylaminopyridine (DMAP) in methylene chloride at xe2x88x9230xc2x0 C. to give doubly protected clarithromycin 8. Further treatment of 8 with sodium hexamethyldisilazane and carbonyldiimidazole in tetrahydrofuran (THF) at xe2x88x9278xc2x0 C. gave cyclic carbonate 19. Cyclic carbonate 19 was subsequently subjected to xcex2-elimination with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in refluxing benzene to give protected enone 6 in excellent yield.
According to the invention the protected enone (6) is then further reacted as depicted in reaction scheme 2
wherein the symbols are as defined above. xe2x80x9cAcxe2x80x9d refers to an acetyl protecting group and xe2x80x9cBzxe2x80x9d refers to a benzyl group.
The hydroxy group at position 12 of compound 6 is esterified by treatment with an appropriate carboxylic acid (R1COOH), N,Nxe2x80x2-dicylohexylcarbodiimide (DCC) and N,Nxe2x80x2-dimethylaminopyridine (DMAP) in a chlorinated solvent such as methylene chloride or dichloroethane (reaction A). Following extractive work up, the crude product is purified by flash chromatography to give the corresponding ester with the general formula IV.
The same compound can be obtained in an alternative way by the following two reaction steps:
Compound 6 is esterified with a 2-haloacetic acid such as chloroacetic acid or bromoacetic acid (reaction B) under identical conditions as described above in reaction A to give haloacetyl derivative IX.
Haloacetyl derivative IX is then treated with a suitable thiol (R1H) in the presence of a base such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), K2CO3, NEt3, in acetone until no starting material remains (reaction C). The reaction typically lasts from 30 minutes to 3 hours. Following aqueous work up, the crude material is purified by silica gel flash chromatography to give the product IV in high yield. In a similar way, treatment of haloacetyl derivative IX with a tetraalkylammoniumcyanide such as tetraethylammoniumcyanide results in the formation of a compound with formula I wherein R1 is xe2x80x94CN.
Compound IV is then treated with an alkali metal base such as NaH or potassium tert.-butoxide in an aprotic solvent such as dimethylformamide (DMF) or tetrahydrofuran (THF) at temperatures ranging from xe2x88x9220xc2x0 C. to 20xc2x0 C. for 30 minutes to 5 hours (reaction D) until no starting material remains as judged by thin layer chromatography (TLC). The amount of base is usually 1 to 3 equivalents relative to the starting compound. The reaction mixture is then partitioned between diethylether and 0.5 M KH2PO4. The crude material isolated from the extraction step is further purified by silica gel flash chromatography to give the product V as a mixture of two diasteromers in various ratios.
Selective cleavage of the cladinose moiety of V is carried out by the methods known to the art with 1 to 5% HCl in an alcolholic solvent such as methanol or ethanol for 12 to 72 hours at a temperature preferably from xe2x88x9215xc2x0 C. to 40xc2x0 C. (reaction E). The solvent is then removed and the crude product is taken up in an appropriate organic solvent. The solution is washed with a basic aqueous solution ranging from pH 8-13. The crude product obtained from the extraction step is then further purified by silica gel flash chromatography to give VI as a mixture of two diasteromers in various ratios.
Oxidation of VI is carried out with 1,2-dichloroethane EDC.HCl, dimethoxy-sulfoxide (DMSO) and pyridinium trifluoroacetate in a chlorinated solvent such as methylene chloride or dichloroethane at temperatures ranging from xe2x88x9215xc2x0 C. to room temperature for 1 to 5 hours as described by Agouridas et al. in J. Med. Chem. 1998, 41, 4080-4100, (reaction F). The reaction mixture is then quenched with NaHCO3-solution, separated from the aqueous phase, dried and evaporated to give the crude product that is further purified by silica gel flash chromatography to give ketolide VII as a mixture of two diasteromers in various ratios.
The oxidation of VI can also be carried out using (1,1,1-triacetoxy)-1,1-dihydro-1,2-benziodoxol-3-(1H)-one (Dess-Martin reagent) in a chlorinated solvent such as methylene chloride at temperatures ranging from xe2x88x9220xc2x0 C. to room temperature for 1 to 5 hours as described by S. F. Martin et al. in J. Am. Chem. Soc 1997, 119, 3193-3194.
Final deprotection of the 2xe2x80x2-hydroxy group of VII is achieved by stirring the compound in an alcoholic solvent such as methanol or ethanol for 12 to 72 hours (reaction G). The solvent is evaporated to give the desired deprotected product of formula I as a single diasteromer.
The following examples illustrate the present invention, but are not intended to be limiting in any manner.
Certain abbreviations are used repeatedly in the following specification. These include:
TLC for thin layer chromatography;
HPLC for high performance liquid chromatography;
DMSO for dimethylsulphoxide;
DBU for diazabicycloundecane;
DIPEA for diisopropylethylamine (Huenig""s base);
DIAD for diisopropylazadicarboxylate;
DMF for dimethylformamide;
THF for tetrahydrofurane;
DCC for dicyclohexylcarbodiimide;
DMAP for 4-dimethylaminopyridine;
EDC.HCl for N-(3-dimethylaminopropyl)-Nxe2x80x2-ethylcarbodiimide hydrochloride;
Rf indicates the retention of the compound on thin layer chromatography;
KOtBu for potassium tert.-butylate;
MS for mass spectrometry;
NMR for nuclear magnetic resonance;
ISP for ion spray.